MANILA, April 28 (Reuters) - President Barack Obama said the United States will on Monday impose new sanctions on Russia targeting individuals and companies over the crisis in Ukraine, a move expected to be followed by separate punitive measures from the European Union.

Obama said the latest sanctions would restrict some high-tech exports to Russia's military, and he warned that a future phase could bring broader "sectoral" sanctions against Russian industries such as banking and defence if Moscow waged further "aggression" against Ukraine.

"Later today there will be an announcement made and I can tell you it will build on the sanctions already in place," Obama told a news conference in Manila during a visit to the Philippines. "These sanctions represent the next stage in a calibrated effort to change Russia's behaviour."

The moves, which the White House said would hit "cronies" of Russian President Vladimir Putin, are aimed at punishing Moscow for not living up to an agreement to defuse the situation in eastern Ukraine, where armed pro-Russian separatists seized about a dozen government buildings.

But Obama acknowledged that there was no guarantee the sanctions would work.

"We are keeping in reserve additional steps that we could take should the situation escalate further," he said on the final stop of a week-long four-nation Asia tour.

He said the next step would be so-called sectoral sanctions that would be "more broad-based".

The European Union is also expected to announce sanctions as early as Monday targeting individuals and companies. Washington is more hawkish on further sanctions than Brussels, which has caused some impatience among some U.S. officials with the European response.

Obama said that in working to mobilize the international response to Russia's takeover of Ukraine's Crimea region, he had to draw into the sanctions push European countries "many of whom have been sceptical to do anything".

The leaders of the Group of Seven (G7) major economies agreed on Saturday to swiftly impose further sanctions on Russia over the Ukraine crisis.

The United States and European Union previously imposed limited sanctions on Russian officials over Moscow's annexation of Crimea. (Additional reporting by Rosemarie Francisco; Editing by Alex Richardson)